1. Field of the Invention
This invention relates to a position detecting method and device for detecting the position of an object by the use of an image pattern picked up by a television camera or the like.
2. Prior Art of the Invention
A method wherein from within an image pattern taken by a pickup device such as television camera, a certain objective pattern is extracted in a manner to be distinguished from any other pattern or a background pattern, and the position of the objective pattern within the two-dimensional image pattern is found, has heretofore been known as disclosed in, for example, the official gazette of Japanese Patent Application Publication No. 52-14112 and the official gazette of Japanese Patent Application Laying-open No. 52-9133.
This method senses the position of the objective pattern on an object in such a way that a local pattern on the object is used as a standard pattern, that the positional relationships between the standard pattern and the objective pattern are stored in advance, that partial patterns cut out at various positions within the image pattern of a pickup region as are applied by the pickup device are sequentially compared with the standard pattern, and that positional coordinates representative of the most coincident partial pattern are extracted.
With such method, however, the objective pattern is distinguished by finding the position of the local pattern which is the most coincident with the standard pattern within the image pattern of the pickup region, so that in case where a plurality of patterns having the same feature as that of the local pattern exist within the image pattern, only one of them is detected, it being impossible to detect the specified local pattern and to obtain the objective pattern.
In order to make it possible to reliably detect only the specified local pattern even when a plurality of patterns having the same feature as that of the local pattern exist within the image pattern, the following method has been proposed.
The pickup region is divided into a plurality of sections, the positional coordinates of the partial patterns in which the degrees of coincidence between the local patterns cut out and the standard pattern become the maximum are evaluated in the respective sections, the degrees of coincidence not smaller than a predetermined value are extracted, and the positional coordinates of the objective pattern are detected from the relative positional relationships among the plurality of positional coordinates of the partial patterns thus extracted.
With these prior-art methods, however, it is the necessary condition that the objective pattern or the local pattern for detecting the inherent positional relationship exists within the pickup region at the time of detection, and when this condition is not fulfilled, the pickup device or the object needs to be moved. Further, in case where in the positional detection of a pattern on a semiconductor pellet or the like, the image magnifications have been increased on account of the promoted minuteness of the pattern of the object or to the end of enhancing the recognition accuracy, the pickup region contracts relatively to an identical supply deviation, and it becomes less likely that the aforecited condition will be met.